There are two stories that explain why Paris is known as The City of Light (or Ville de Lumière, if you prefer):
The first refers to the 18th century, when police authorities in the city asked that everyone put a lighting candle or oil lamp on their window, so that there would be more light in the streets at night in response to a rising crime rate.
The second version is that Paris became known as the City of Light in 1820 when it adopted a public gas lighting system that had been developed by engineer Philippe le Bon. It wasn’t the first urban centre to use public gas lighting but it was probably the prettiest and the illuminated Parisian streetscapes became a sight not to be missed.
Two hundred years on, Paris still presents a truly pretty picture at night, as can be seen from these wonderful photos.